How do I get my A/C Running again?

Question

Just moved into new house and wanted to put in new programmable thermostat. Followed wiring guide and it didn't work, so I reinstalled the old thermostat and now the heat & a/c don't work. I checked all breakers @ the main service, condo sub-panel and outside of the unit itself. All were okay, but I recycled them just to make sure. What could be the cause and how do I go about fixing before calling tech, if at all possible?

Answer 1

could be possible that there is a control fuse on the board that controls the air handler....an easy test is to remove the wires from the thermostat and connect the red and green wire together. if the fan comes on then there is something else wrong... be sure and write down on paper which wire goes to each terminal on the thermostat....could also be possible that you burnt your transformer up when you connected the new thermostat up wrong....call a reputable hvac tech and have them fix your unit...

Answer 2

Inside the furnace, by the control board, you may have a fuse.

It is like the fusses in a car.

Check if it's still good.

It's easy to check, it is a plastic one, you can see the wire inside.

You may burn the fuse, if you didn't turn the furnace breaker "OF" before changing thermostat.

If this fuse is good, check again connections on your thermostat.

Answer 3

Was it working prior to to change over? Since you just moved in , perhaps the previous owners turned the main shut off switch "off"?

Answer 4

Since the old thermostat didn`t work when reinstalled I would start by looking at the wires just beyond where they attach to the thermostat screws.  The wires are a solid copper wire and all it takes is one hard bend and the wire can break inside the insulation just beyond where it is removed.

Granted this is a stretch but it happened to me once a long time ago and I`ll never forget the troubleshooting nightmare.

Also make sure that any jumpers the programmable thermostat call for are in their proper place.

All this being said assuming that you killed all power to it before switching them out.  Go after the fuse mentioned above if you didn`t.

Answer 5

You may have shorted some wiring and caused a fuse on the circuit board to blow, if you didn't turn the power off before doing the wiring.

This is a low voltage fuse probably located on the circuit board. It will be like a car fuse and probably a 3 amp.

This is my best guess for something you might be able to do.